When an underground pipeline has a damaged part or joint through which a fluid leaks out from the pipeline or underground water leaks into it, it desirable to repair the damaged part or joint to prevent such leakage.
When repairing such a pipeline, it has been usual to repair a long pipeline as a whole by inserting a tubular lining material into the pipeline and hardening the lining material along the inner surface of the pipeline.
Methods for repairing a sewer pipe, for example, involve applying lengthy tubular sheet material, which is prepared from a thickened solution of a curable resin in which high-strength fibers are dispersed, onto the inner surface of the pipeline, bring it into intimate contact with the inner surface of the pipeline and heating it to cure the resin in the sheet material. (see EP-A-454309).
If a long pipeline is only partly damaged, however, it is undesirable from an economical standpoint to line the whole pipeline and it is desirable to repair only its damaged part.
The lining of only a part of a pipeline, such as a damaged part, however, presents different problems from those arising from the lining of the whole pipeline along its entire length.
For example, when lining a sewer pipe by a method as described above, a rigid pipe formed in the pipeline to line it does not necessarily adhere closely to the inner surface of the pipeline. Instead, there is a good likelihood that a clearance may be left between the outer surface of the pipe and the inner surface of the pipeline which will allow the passage of underground water entering the pipeline through its damaged part.
If the pipeline is lined along its whole length, the underground water which has entered the clearance is required to flow a very long distance before leaving it to enter the pipeline, the amount of water entering the pipeline being, therefore, negligible. If the pipeline is only partly lined, however, the distances between its damaged part and the ends of the lining pipe are too short to prevent a large amount of underground water from entering the pipeline and flowing into sewage.
Another problem is that there are not a few cases where the work for lining a pipeline has to be done in the presence of a large amount of underground water which has entered it through its damaged part. Therefore, it is very likely that water may hinder the curing reaction of the resin, or that the cooling action of water may delay the effective heating of the resin and its curing.
Under these circumstances, it is an object of this invention to enable the repairing of a pipeline, such as a sewer, which is limited to a damaged part thereof and, independently, to prevent underground water more effectively from entering the pipeline through its damaged part and past a comparatively short repair pipe section.